1. Technical Field
The present invention relates to a bus interface system, and more particularly to a current mode bus interface system that transmits/receives data currents.
2. Discussion of the Related Art
Generally, to transmit/receive signals between integrated circuits, either a voltage mode transmitting/receiving operation or a current mode transmitting/receiving operation is performed. Since the voltage mode transmitting/receiving operation introduces a resistive-capacitive delay when transmitting/receiving signals, the current mode transmitting/receiving operation has been studied to reduce the resistive-capacitive delay.
In the current mode transmitting/receiving operation, a current of a transmitted/received signal is observed. In particular, the current mode transmitting/receiving operation maintains a voltage level of a transmission line at a predetermined level, and transfers data by changing a level of a current flowing through the transmission line. For example, a transmitter may sequentially transfer digital data using two logic levels ‘1’ and ‘0’. Thus, a current level of about 17 mA through 23 mA may be set to the logic level ‘1’, and a current level of about 0 mA through 6 mA may be set to the logic level ‘0’. A receiver may then recover the transmitted digital data by determining the current level of the transmitted signals. Since the voltage level is maintained at the predetermined level during the current mode transmitting/receiving operation, a resistive-capacitive delay may be reduced.
In a ‘pseudo-differential current mode’ transmitting/receiving operation, the transmitter may transmit a reference current with a data current. For example, the transmitter may set the current level of about 17 mA through 23 mA to the logic level ‘1’, set the current level of about 0 mA through 6 mA to the logic level ‘0’, and transmit the data current based on the set logic levels. At the same time, the transmitter may transmit a reference current of about 10 mA. The receiver receives both the data current and the reference current, compares a magnitude of the data current with that of the reference current, and then determines the logic level of the transmitted data current. Thus, for example, when the magnitude of the data current is larger than that of the reference current, the transmitted digital data is the logic level ‘1’, and when the magnitude of the data current is smaller than that of the reference current, the transmitted digital data is the logic level ‘0’.
In a device embodying a mobile application such as a portable phone, a bus interface can be used to aid in the reduction of power consumption. For example, by causing the bus interface and other components of the device to enter into a suspend mode when they are not being used, the power consumed by the device may be reduced. Accordingly, as various applications and devices such as a mobile phone and a digital camera continue to become integrated, the need to support bidirectional data transfer between a digital camera module and a mobile phone module is increasing. However, because the bus interface is increasingly being used in such devices, the ability to conserve power is lessened. As such, a need exists for a bus interface system that is capable of performing a bidirectional data transfer between a host and a client while reducing power consumption.